Sea Squirts Sucking Up Species

  • A colony of tunicates in Guam (Photo by David Burdick, courtesy of NOAA)

Slimy, hungry invaders are moving through
the waters off the Northwest coast of the US.
They’re called invasive tunicates –
or sea squirts. And they’re the same invasive
species that devastated shellfish farms on Canada’s
east coast. If invasive tunicates aren’t controlled,
you could see a lot of seafood options disappear
from markets and menus. Ann Dornfeld has the story:

Transcript

Slimy, hungry invaders are moving through
the waters off the Northwest coast of the US.
They’re called invasive tunicates –
or sea squirts. And they’re the same invasive
species that devastated shellfish farms on Canada’s
east coast. If invasive tunicates aren’t controlled,
you could see a lot of seafood options disappear
from markets and menus. Ann Dornfeld has the story:

It’s a peaceful spring morning at this suburban marina. But beneath the water’s surface, a hunt is
underway.

(water sounds)

Professional divers – like Jesse Schultz with the Washington Department of Fish and Wildlife – are
combing the docks for invasive tunicates. They don’t have to look far.

“That’s one of the tunicates right there – that’s the guy right there.”

Schultz surfaces holding a jelly-like tube. Sea squirts compete with everything from clams to tube
worms for the plankton they all eat. The sea squirts usually win, because they don’t have native
predators. Three species came here from Asia, probably on boat hulls. Today, divers are cleaning
the hulls of local boats to keep the sea squirts from spreading.

Allen Pleus manages invasive species for the state.

“The whole intent right now is a containment action. We want to prevent any of these boats
from leaving this harbor with the tunicates attached to their bottom, going to another
harbor, and infesting that harbor or marina.”

When invasive tunicates get to a new harbor, they quickly become the dominant species. In the
warm part of the year, they spawn every 24 hours. And along with hogging the food supply, one
species of sea squirts forms a slimy mat that smothers mussels and other shellfish.

Pleus says if tunicates get out of hand, they could make a big impact on the seafood industry.

“It can definitely affect especially shellfishing in this area. Puget Sound, Western Washington is one of
the largest producers of shellfish in the nation. It could also affect other populations of
food fish, including salmon, by taking out a lot of the nutrients that juvenile salmon feed
on.”

Nova Scotia learned that lesson the hard way. Pleus says in Eastern Canada, entire shellfish
farms were recently wiped out by invasive tunicates.

“So the rap sheet is clear. They can grow to exponential sizes, quantities and smother
aquaculture facilities. They can’t even lift up their lines it’s so heavy with these critters on
it.”

To prevent the same thing from happening here, the state workers have to move quickly – and
they have to be thorough.

“Here’s another bag, Justin!” (splashing sound)

Back in the water, diving biologist Jesse Schultz has his hands full with a boat that has apparently
been docked for seven years. Its tabs show that’s the last time it was registered.

“This guy’s getting a free boat cleaning, sort of!”

The state is trying to scrape clean every infested boat in Puget Sound before the summer boating
season. But Schultz says because the docks are still covered with invasive tunicates, they’ll grow
back on this boat if the owner doesn’t keep it clean.

“That’s the biggest thing these guys can do to keep these things from spreading is have
their boats maintained.”

The state is still figuring out the best way to clean the docks. So far biologists have cleaned only
one entirely. When they were done, they’d removed ten tons of critters.

Unfortunately, Allen Pleus says only some of those were tunicates. In order to get rid of the
invasive sea squirts, they have to employ a sort of scorched earth policy.

“That is one of the hardest parts of this is that we have to basically take everything out.”

That means the good with the bad. We sift through a bucket of the creatures scraped from the
dock. Along with plenty of invasive tunicates, there are brightly colored sea cucumbers, scallops,
mussels, rock oysters, feather duster worms and chitons – exactly the kinds of animals the state
is trying to protect. They have to destroy the habitat in order to try to save it.

For The Environment Report, I’m Ann Dornfeld.

Related Links

Great Lakes Record Lows

  • Lower water levels on the Great Lakes make some channels such as the Muskegon River too shallow for big freighters to enter fully loaded. (Photo by Lester Graham)

The Great Lakes are hitting new record low water levels. The water is so low that
big 1000-foot cargo ships are running aground. There’s debate about
whether this is just part of the historic ups and downs of the Great Lakes, or if it’s the
effects of global warming. Lester Graham reports from Lake Michigan’s Muskegon
River, a trouble spot for some of the big ships:

Transcript

The Great Lakes are hitting new record low water levels. The water is so low that
big 1000-foot cargo ships are running aground. There’s debate about
whether this is just part of the historic ups and downs of the Great Lakes, or if it’s the
effects of global warming. Lester Graham reports from Lake Michigan’s Muskegon
River, a trouble spot for some of the big ships:


Here at the end of the pier next to the lighthouse, it’s cold, it’s icy and it’s windy. And
it’s hard to imagine a ship navigating its way into this channel, but ships do on a
regular basis to bring coal to a power plant. This year, however, some of the ships
have ended up aground here simply because of lower lake levels and more sediment
in the channel:


“There’s been three this summer here in Muskegon. They go hard up on the sand.”


Dennis Donahue is the marine superintendent for the National Oceanic and
Atmospheric Administration’s Lake Michigan field station at Muskegon, Michigan. He
says this year’s groundings of cargo ships just hasn’t happened that often in the
past:


“Well, we haven’t had a grounding here, certainly in the last 15 years due to water
levels.”


Lester Graham: “So what’s happening here? What’s going on?”


Donahue: “Well, there’s a couple of things, we’ve got the water levels dropping and
then we’ve got some weather patterns that are carrying sediment to the mouth of the
Muskegon River. So, those two compound and create shoal areas.”


So lower water and a rising bottom mean channels are more shallow. That means
ships have to carry less cargo, and that costs the shippers reportedly a million
dollars per ship per year.


Scientists have been monitoring the dropping lake levels for close to a decade now.
At NOAA’s Great Lakes Environmental Research Lab, Deputy Director Cynthia
Sellinger says she’s been seeing a trend in the weather that’s causing the problem:


“We’re having a lot less precipitation and a lot more evaporation. And that’s
impacting the water levels on the lake.”


Less snow pack and rain mean less water filling the lakes, and with warmer winters
Sellinger says there’s less ice cover to protect the lakes from massive evaporation.
Historically, about 50% of the lakes’ surfaces have been covered by ice. These
days, it’s more like ten to 20%. Cold air hits the warmer water and
carries it away. For Lake Superior alone, a one-inch drop is more than 500 billion
gallons. During the past decade, Superior has lost nearly 13 trillion gallons.


“The upper lakes, Superior, Michigan and Huron, are very close to their record low.
So, it’s approaching an extreme. Superior reached its record low in 1926 and just
this year it broke the record low for September. So, 2007 now is a new record low
for Lake Superior. Lakes Michigan and Huron are approaching their record low.”


Sellinger and her colleagues are not ready to say global warming is causing the
lower lake levels. It might just be a part of a long cycle of ups and downs of the lakes.
But the lower water levels do fit some of the computer model predictions about
global warming.


Lower lake levels causing problems for big cargo ships and marinas catering to
recreational boaters are problems enough. But, some environmentalists say if lower
water levels are caused by global warming, the pressures on the water in the Great
Lakes likely are going to get a lot worse. Andy Buchsbaum heads up the National
Wildlife Federation’s Great Lakes office:


“The hidden threat of global warming is that not only does it affect Great Lakes water
levels simply because of increased evaporation or increased temperatures changes
precipitation, but the threat it makes to Great Lakes water levels is even greater.
Because global warming, global climate change, is having massive effects already
and is likely to have even greater effects on water supplies in the Southwest, the
Southeast and all over the country. And as those pressures increase, the pressure
to divert Great Lakes water will increase exponentially.”


We don’t know whether new diversions to dry areas of the country could cause as
much of a problem as less precipitation and more evaporation of the Great Lakes
already do. But, it would certainly aggravate the problem. The effects of water
levels dropping further mean more economic hardship for shipping and tourism. And
environmentalists say ecological damage to coastal habitat that fish and other
wildlife need to survive could be on a scale that’s not been seen on the Great Lakes
in recorded history.


For The Environment Report, I’m Lester Graham.

Related Links

Lake Levels Scrape Bottom

Much of the industry in the nation’s mid-section relies on
shipments of raw materials on the Great Lakes. Great Lakes ports in the
U-S and Canada handle more than 200-million tons of material annually.
The Lakes are also a source of water and recreation for nearly a third
of
the nation’s population. But, during the last two years, water levels
have
been falling at a record breaking pace. The Great Lakes Radio
Consortium’s Lester Graham reports: